I was in almost the same situation, but not for a long time ;-)
I quickly realized that as long as I put into the HL all the options I want(fog lights, roof rack, sun-roof etc.), the price becomes quiet the same. Even when I negotiated almost $3K it was still pretty close to Premium without Navi at sticker. At least in my case I couldn't get $5K difference that I wanted to get at least. Then when I got a final price I compared what I'm gonna get and at that point it was clear to me that only one good reason to get a HL was - much faster delivery. Okay, second one was - it's built at the same factory in Japan where RX is built so quality has to be very good.
In term of features - no comparison for such a small difference in $$:
1. less powerful engine(I even did not consider 4 cyl - 2WD version, since to me this is a BS);
2. no 2 zone A/C
3. no 3rd row seats.
4. less cargo space.
5. less comfortable seats
6. no Navi(was) available.
7. better warranty for MDX + TLC
It doesn't mean everybody has to agree with me, but to me it was enough.
Granite Green 2002 Premium w/Navigation driven home on 11/20